Nigeria’s Muslim cleric Sheikh Ibrahim al-Zakzaky has headed for India to receive treatment as his health condition is deteriorating after spending four years in detention along with his wife, who was also injured during a crackdown by Nigerian authorities in 2015.

RNA - The 66-year-old cleric, along with his wife Zinat, embarked on a journey to India on Monday, the Information Nigeria news outlet reported.

It added that earlier in the day, the couple was heavily escorted by armed security forces of Nigeria’s domestic intelligence agency, Department of State Services (DSS), from their residence in the city of Zaria to the airport in the capital Abuja, where they could fly to India.

Sheikh Zakzaky, the leader of the Islamic Movement in Nigeria (IMN), is also being accompanied by some officials of security services as well as medical personnel, while travelling to India, the report further said.

The top cleric has been in detention since December 2015 after his home in Zaria was brutally raided by Nigeria’s forces, during which he was beaten and lost his left eye.

During the violent crackdown, three of his sons lost their lives, his wife sustained serious wounds and more than 300 of his followers were killed.

According to Press TV, Sheikh Zakzaky was charged in April 2018 with murder, culpable homicide, unlawful assembly, disruption of public peace and other accusations. He has pleaded not guilty, vehemently rejecting all accusations brought up against him by his country's authorities.

Last week, a Nigerian court granted the Muslim cleric bail so that he could fly to India for treatment.

The Islamic Human Rights Commission (IHRC), based in London, said last month that the cleric’s health condition had further deteriorated, since he was reportedly poisoned in prison.

At the time, his son, Mohammad, said that he was shocked by his father’s worsening medical condition after visiting him, stressing that he needed to be immediately hospitalized as “large and dangerous quantities of lead and cadmium have been found in his blood.”

Recently, a Nigerian court granted the government permission to label the IMN as a "terrorist" group, a move that many believe would give officials the opportunity to clamp down harder on it.

IMN members regularly take to the streets of the Nigerian capital to call for the release of Sheikh Zakzaky.

During the past couple of weeks, several demonstrators have been killed after Nigerian troops used live ammunition and tear gas. The IMN says it has lost at least 20 of its members during the clashes.

In 2016, Nigeria’s federal high court ordered Sheikh Zakzaky’s unconditional release from jail following a trial, but the government has so far refused to set him free.